• Journal of KIISE:Computer Systems and Theory
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• v.27 no.1
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• pp.61-67
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• 2000

Digital controllers found in many industrial real-time systems consist of a number of interacting periodic tasks. To sustain the required control quality, these tasks possess the maximum activation periods as performance constraints. An essential step in developing a real-time system is thus to assign each of these tasks a constant period such that the maximum activation requirements are met while the system utilization is minimized [1]. Given a task graph design allowing producer/consumer relationships among tasks [2], resource demands of tasks, and range constraints on periods, the period assignment problem falls into a class of nonlinear optimization problems. This paper proposes a ploynomial time approximation algorithm which produces a solution whose utilization does not exceed twice the optimal utilization. Our experimental analysis shows that the proposed algorithm finds solutions which are very close to the optimal ones in most cases of practical interest.

• The Transactions of the Korea Information Processing Society
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• v.3 no.5
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• pp.1070-1081
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• 1996

In this research, a model was developed for estimating the queue length of vehicles, based on occupancy time of each vehicle collected by loop detectors which were setup at the upstream of urban street. The estimation model suggestes a method which minimizes architectural effects of the street, such as existence of pedestrian crossing, for future applications to the field. The estimation model suggested in this research was established based on real traffic data collected at up-stream detectors in Kangnam Subway station, Seoul, and the formula of the model is based on Multi-Polynomial equations. Consequence of the experiments showed that the model can adequately and in real-time mode measure length of the queue which were constructed at the 80 to 90 meters away from the upstream detectors. The estimation accuracy of the model was verified in statistical analysis conducted by regressing analysis and test results in real traffic situation.

• Journal of Korean Society for Geospatial Information Science
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• v.18 no.4
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• pp.109-117
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• 2010

The ultimate purpose of this study is to propose a method to improve water supply management efficiency which is one of the two main approaches to solve the water supply-related problems. As an effort, targeting commercial water, a series of efforts was performed such as choosing a field area, selecting a sensing point, installing a sensor and server systems, and monitoring the real time data. Through the analyses of the real time data gathered, a series of water consumption trend analysis models were developed for each day and for each month. And Also proposed are the related utilization of the developed trend analysis models and a GIS. As a result of the aforementioned research, the proposed trend analysis technique is expected to offer some important role for the water supply forecasting agministation and management.